"Frank Gilliland" wrote in message
...
Everyone will think I'm insane for saying this, but Landshark has it
right.

No he doesn't.

In order for co-phased antennas to achieve that ideal figure-8
pattern they must be nearly ideal antennas, which CB antennas are not.

They don't nessessarly need be to be ideal, but the do need to be installed
the same way. By the way no antenna is ideal, but many people have a lot of
success anyway.

Landshark's link explains why this happens. I wouldn't expect any
significant improvement in the omnidirectional characteristics of
dualies (as the site claims), but I do know they don't provide any
noticable directional gain.

If you check the link I provided you will see there is some gain. The gain
does not become noticeable until you have at least a 1/4 wavelength
separation, and at that it is around 2 db or so. On the site I posted the
link for you will see the figure 8 pattern becomes very noticeable for a
half wavelength between antennas. Getting to that degree of separation is
much easier to do on a semi because of their size, and the fact the antennas
are further apart from being mounted on the side view mirrors. Passenger
vehicles just don't have the size needed.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

"Leland C. Scott" wrote in message
...

"Frank Gilliland" wrote in message
...
Everyone will think I'm insane for saying this, but Landshark has it
right.

No he doesn't.

Of course I do Leland, you just don't want me too

In order for co-phased antennas to achieve that ideal figure-8
pattern they must be nearly ideal antennas, which CB antennas are
not.

How would you know Leland? Remember, you don't like
CB, let alone talk or use or own one.

They don't nessessarly need be to be ideal, but the do need to be
installed
the same way. By the way no antenna is ideal, but many people have a lot
of
success anyway.

Landshark's link explains why this happens. I wouldn't expect any
significant improvement in the omnidirectional characteristics of
dualies (as the site claims), but I do know they don't provide any
noticable directional gain.

If you check the link I provided you will see there is some gain. The gain
does not become noticeable until you have at least a 1/4 wavelength
separation, and at that it is around 2 db or so. On the site I posted the
link for you will see the figure 8 pattern becomes very noticeable for a
half wavelength between antennas.

The point was that it was a much better omni-directional pattern
on Dual antenna's, to which that is achieved. You are saying
that Signal Engineering, which soul business is antenna's is wrong,
good luck on trying to convince others of that.


Getting to that degree of separation is
much easier to do on a semi because of their size, and the fact the
antennas
are further apart from being mounted on the side view mirrors. Passenger
vehicles just don't have the size needed.


--
Leland C. Scott
KC8LDO


Landshark


--
The world is good-natured to people
who are good natured.

"Landshark" wrote in message
m...

"Leland C. Scott" wrote in message
...

"Frank Gilliland" wrote in message
...
Everyone will think I'm insane for saying this, but Landshark has it
right.

No he doesn't.

Of course I do Leland, you just don't want me too

Then explain away the the information on the other site. Get a copy of EZNEC
and model it yourself.

http://www.eznec.com/

And if you're to cheap to buy a copy then try the freebee versions at:

http://www.qsl.net/wb6tpu/swindex.html

Then you can check at the site below for antenna modeling tips and
information about many types of antennas from an expert in the area.

http://www.cebik.com/

And another interesting antenna site:

http://www.antennex.com/


In order for co-phased antennas to achieve that ideal figure-8
pattern they must be nearly ideal antennas, which CB antennas are
not.

How would you know Leland? Remember, you don't like
CB, let alone talk or use or own one.

You have been sleeping at the keyboard. I was on CB back in the late 70's
until I got fed up with all of the jerks on the air. Even ran a mobile
AM/SSB system. I used a Midland combo base- mobile radio. At that time the
rigs were 23 channels. I've been there, done that, and gave away the radio
to my nephew some years ago.


They don't nessessarly need be to be ideal, but the do need to be
installed
the same way. By the way no antenna is ideal, but many people have a lot
of
success anyway.

Landshark's link explains why this happens. I wouldn't expect any
significant improvement in the omnidirectional characteristics of
dualies (as the site claims), but I do know they don't provide any
noticable directional gain.

If you check the link I provided you will see there is some gain. The
gain
does not become noticeable until you have at least a 1/4 wavelength
separation, and at that it is around 2 db or so. On the site I posted
the
link for you will see the figure 8 pattern becomes very noticeable for a
half wavelength between antennas.

The point was that it was a much better omni-directional pattern
on Dual antenna's, to which that is achieved. You are saying
that Signal Engineering, which soul business is antenna's is wrong,
good luck on trying to convince others of that.

They also make antennas for money. And when money is involved you have to
suspect the claims they make. It won't be the first nor the last time a
manufacture stretched the truth, i.e. lied. But then again you guys also
believe Class "C" amplifiers are linear, "magic" lenghts of coax to fix
antenna SWR etc. This news group should be named "rec.voodoo.11m.radio" from
all of the crap that's passes for fact.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

"Leland C. Scott" wrote in message
...
This news group should be named "rec.voodoo.11m.radio" from
all of the crap that's passes for fact.

Here's a fact................Al Banys says you like men for sex
partners....buttboy.

In , "Leland C. Scott"
wrote:


"Landshark" wrote in message
om...

"Leland C. Scott" wrote in message
...

"Frank Gilliland" wrote in message
...
Everyone will think I'm insane for saying this, but Landshark has it
right.

No he doesn't.

Of course I do Leland, you just don't want me too

Then explain away the the information on the other site. Get a copy of EZNEC
and model it yourself.


Forget about all that antenna-modeling software crap and build a
simple field-strength meter. Then go measure it yourself because
that's how it's done in the real world, and that's how the page at
Landshark's link came up with the radiation pattern for the
bumper-mount antenna. A similar pattern can be found in almost any
radio-communications handbook that covers mobile antennas.






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In , Frank Gilliland
wrote:

snip
... A similar pattern can be found in almost any
radio-communications handbook that covers mobile antennas.


Including Radio Shack's famous tome, "All About CB Two-Way Radio"
which, IMO, should be the rrcb FAQ by proxy.







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"Frank Gilliland" wrote in message
...
Forget about all that antenna-modeling software crap and build a
simple field-strength meter. Then go measure it yourself because
that's how it's done in the real world,

Have you personaly done so for the setup in question?

and that's how the page at
Landshark's link came up with the radiation pattern for the
bumper-mount antenna. A similar pattern can be found in almost any
radio-communications handbook that covers mobile antennas.

The antenna simulation software shows the same thing as single bumper mount
antenna pattern as on the page Landshark posted. That's why I question the
omni pattern for a dual antenna setup. In fact Frank you can look up the
pattern for such a setup, dual antenna, in a copy of the radio engineer's
handbook, and I'm surprised you haven't since you know about it. More than
one Ham has modeled some commercially manufactured antennas and discovered
they don't perform as the ads suggest. When the manufacture was confronted
with the results they modified their claims. The software modeling approach
works or people wouldn't waste their time with it. In fact more antenna
manufactures are doing it since it saves a lot of screwing around making
error prone measurements with a field strength meter, and that's how they
are doing it now in the real world.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

"Leland C. Scott" wrote in message
...

"Frank Gilliland" wrote in message
...
Forget about all that antenna-modeling software crap and build a
simple field-strength meter. Then go measure it yourself because
that's how it's done in the real world,

Have you personaly done so for the setup in question?

Stick to your 2 meter handheld...gayboy.

In , "Leland C. Scott"
wrote:


"Frank Gilliland" wrote in message
.. .
Forget about all that antenna-modeling software crap and build a
simple field-strength meter. Then go measure it yourself because
that's how it's done in the real world,

Have you personaly done so for the setup in question?


Over the years I have tested many different antenna installations,
both on my own vehicles and at customer request. Here are a few that I
remember:

Just last month I tested a 4' helical mounted on the center of the
roof of a pickup. It showed a little gain to the front and rear, kinda
like what people are trying to achieve with dualies.

Another was a dual-antenna setup on a tractor cab. I don't remember
the make but they were short, center-loaded whips on the mirrors.
Almost no signal to the rear with or without the trailer, moderate
signal to the front and sides.

On the same truck (at a later date) was mounted a single 66" whip from
RS on the passenger-side mirror. This was goofy: it was generally omni
with a little gain to the front-left and right-rear, and there was
-no- expected dead-zone to the left-rear (possibly due to the antenna
height). Pretty good antenna! As far as I know he still uses it.

Tested dual 9' whips on the bumper of a very sweet GMC pickup (1-ton
custom job, diesel, fording package....the works!). Pattern was almost
perfectly omni. EXCELLENT SIGNAL STRENGTH!!!

I also tested my own truck with different antennas. The mount is
centered on the roo-guard. It almost always shows a slight gain to the
sides, but is generally omni.

I have tested more and with different types of radios (lots of VHF),
but I can't remember all of them offhand, and I don't feel like typing
all day. I should mention that I chose the location for the antenna
mount on my truck (on the front at hood level) because it was the
location with the best RF ground, as tested with my GDO. This is the
case for -my- truck. I wouldn't extrapolate that for any other
vehicle. In fact, the other day I was going over the Chevy (S-10) with
the GDO looking for a good spot for an antenna mount, and the spot
that works so well on the Dodge is -not- a very good RF ground on the
Chevy. No antenna modeling software can predict something like that.

BTW, the easiest way to do a pattern test is to park the meter with a
spotter a couple hundred feet away, drive the test vehicle in a tight
circle, stop every ten degrees, key up and transmit the heading. It
takes all of ten minutes, give or take, depending on how fast your
spotter can read the meter and write down the data.

And I still don't understand the desire for front/back gain on a
vehicle. Unless you drive most of the time on the long, straight
highways of the desert and plains, a directional pattern isn't going
to do much good at all, and what little bit gain you can get from a
directional pattern won't amount to anything you can hear from the
speaker. Oh well, to each his own. As for me, I'm going to try dual 9'
whips on the rear bumper of the GMC.


and that's how the page at
Landshark's link came up with the radiation pattern for the
bumper-mount antenna. A similar pattern can be found in almost any
radio-communications handbook that covers mobile antennas.

The antenna simulation software shows the same thing as single bumper mount
antenna pattern as on the page Landshark posted. That's why I question the
omni pattern for a dual antenna setup. In fact Frank you can look up the
pattern for such a setup, dual antenna, in a copy of the radio engineer's
handbook, and I'm surprised you haven't since you know about it. More than
one Ham has modeled some commercially manufactured antennas and discovered
they don't perform as the ads suggest. When the manufacture was confronted
with the results they modified their claims. The software modeling approach
works or people wouldn't waste their time with it. In fact more antenna
manufactures are doing it since it saves a lot of screwing around making
error prone measurements with a field strength meter, and that's how they
are doing it now in the real world.


Antenna modeling software is a great tool for learning theoretical
antenna design. But unless the software was written by a team of grad
students at Cal-Tech and runs on Big Blue, it cannot possibly account
for all the variables involved. It is not, and should not be used as,
a substitute for actual field measurements.






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"Frank Gilliland" wrote in message
...
BTW, the easiest way to do a pattern test is to park the meter with a
spotter a couple hundred feet away, drive the test vehicle in a tight
circle, stop every ten degrees, key up and transmit the heading. It
takes all of ten minutes, give or take, depending on how fast your
spotter can read the meter and write down the data.

My reason for asking is the pattern is of course 3d. Doing an elevation
slice through the pattern I have seen extensive variation in the pattern as
the elevation slice is moved up and down in the z-axis when multiple
elements are involved. Normally the main lobe in the field pattern is not at
90 degrees to the vertical antenna, but tilted up by some number of degrees.
Standing at ground level a few hundred feet away doesn't really give you a
good idea of the of what the field pattern looks like.

And I still don't understand the desire for front/back gain on a
vehicle. Unless you drive most of the time on the long, straight
highways of the desert and plains,

Long haul truckers spend a lot of their time driving over long sections of
straight highways.

a directional pattern isn't going
to do much good at all, and what little bit gain you can get from a
directional pattern won't amount to anything you can hear from the
speaker.

Tell a hard core Dxer that a db or so difference don't matter and see what
happens. They will swear up and down it does.

Oh well, to each his own. As for me, I'm going to try dual 9'
whips on the rear bumper of the GMC.

A buddy of mine used a 4-point mag-mount on the roof of his car to hold a 9
foot whip when he was on 11m years ago. He claimed around 100+ miles with a
standard radio.

Antenna modeling software is a great tool for learning theoretical
antenna design. But unless the software was written by a team of grad
students at Cal-Tech and runs on Big Blue, it cannot possibly account
for all the variables involved. It is not, and should not be used as,
a substitute for actual field measurements.

I think if you contact Mr. Cebik, W4RNL, you will find he does both, model
and test. Seems his models predict real antenna performace rather well. If
he didn't then there would be no way to advise others about areas that
require care when modeling atennas. Also Roy, W7EL, has a lot of experience
too.

I worked with Mr. Cebik on a Turnstile matching idea. As he pointed out in
an article in QEX the schema has the draw back of producing a gain variation
of around 2 db from perfect omnidirectional. While not a big deal it can be
improved by a small adjustment to the length of the phasing lines that do
the impedance match at the expense of a small increase in SWR. The
analytical solution was confirmed by the antenna simulation software, which
showed an improvement in pattern circularity and equal currents in the
antenna elements.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft